Air quality expert group - Fine particulate matter (PM2.5) in ... - Defra

PM2.5 in the UK
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37. Further consideration of all these aspects of emission inventory uncertainties can
be found in Annex D of the report Evaluating the Performance of Air Quality
Models (Defra, 2010) which gives some detail of the uncertainties in the spatial
and temporal variability in emissions in the context of modelling uncertainties.
38. The NAEI only estimates emissions from sources which need to be included
in national inventory reporting under various international commitments
(e.g. CLRTAP) and/or where at least some information is available to make
a reasonable estimate. Gaps in the inventory largely occur where there is
insufficient source activity information available to make an estimate of
emissions. In recent years, the NAEI has closed many of the gaps in the
inventory for anthropogenic and some natural sources, but acknowledges the
very high levels of uncertainties associated with some of their estimates, e.g.
for bonfires, small-scale burning of waste, natural fires, etc. However, a number
of gaps still remain in specific areas or for some additional processes in sectors
which are already covered in the inventory. These include emissions from:
• certain arable farming processes and harvesting;
• domestic cooking and barbecues;
• building demolition processes;
• certain quarrying processes such as blasting and filling of used quarries;
• certain fugitive emissions in the metals industry (e.g. smelting); and
• use of munitions by military operations and for quarrying.
39. Without constructing an inventory, it is impossible to judge the magnitude
of these emissions, but the sources are ranked above in an anticipated
decreasing order of importance to emissions on a national scale. However, in
some locations and at certain times, these sources could make a significant
contribution to local emissions, e.g. from building demolition.
4.3 Quantifying the emissions of PM2.5 precursor gases,
their conversion to particles and their spatial
distribution
40. Emissions of PM2.5 precursor gases from anthropogenic sources in Europe
are also estimated by inventories and reported by countries to CLRTAP. The
NAEI provides a time series for UK emissions of the precursors NOx, SO2, nonmethane
volatile organic compounds (NMVOCs) and NH3 from 1980-2009 and
projections to 2020. These four pollutants are those covered under the National
Emission Ceilings (NEC) Directive which sets national emission ceilings for each
of these pollutants for EU member states to be met by 2010. Emissions are
estimated in the same way as for PM2.5 using sector-specific emission factors
and activity data.